Small study raises questions about procalcitonin treatment algorithms

Action Points

Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Note that this retrospective study found a higher-than-expected readmission rate among individuals with pneumonia treated conservatively in the context of a low procalcitonin level.

Further validation studies of procalcitonin-based antibiotic dosing may be needed.

MONTREAL -- Treating community-acquired pneumonia on the basis of a biomarker that's associated with disease severity might not always yield positive results, a researcher said here.

In a retrospective analysis, pneumonia patients with low levels of the protein procalcitonin -- and treated accordingly, based on guidelines -- had higher-than-expected relapse rates, according to Simon Waghchoure, MD, of Miriam Hospital in Providence, RI.

The finding is surprising because treating patients on the basis of procalcitonin levels has been shown to reduce the use of antibiotics with no increase in mortality, Waghchoure reported at the annual CHEST meeting.

Procalcitonin is a soluble protein that's part of the response to severe systemic inflammation and in particular is a marker of bacterial infections, Waghchoure noted.

Current guidelines suggest that antibacterial treatment can be adjusted based on procalcitonin levels in patients with sepsis, he added, with studies showing that low levels of the protein mean antibiotic doses can be de-escalated without an increased risk of death.

But he and a colleague wondered how that translated into an important clinical outcome -- 30-day readmission after discharge for pneumonia.

The issue is important because readmissions are costly -- for pneumonia, it's about $13,000 a case -- and about one in five patients discharged after treatment for the disease is readmitted within a month, making up about 6.3% of all readmissions, he noted.

To help clarify the issue, the investigators looked at records for a year before and a year after their institution began using a procalcitonin-guided (PCT) algorithm to help in treating pneumonia patients in November 2013.

In essence, he reported, the algorithm suggested that pneumonia patients with procalcitonin of at least 0.25 nanograms per milliliter should complete a five-day course of antibiotics even if the level were falling.

On the other hand, antibiotics could be stopped if the level was below 0.25 nanograms per milliliter.

From Nov. 1, 2012 to Oct. 31, 2013 -- the year before PCT testing was available -- 79 of 655 pneumonia patients, or 12.1%, were readmitted within 30 days. By comparison from Nov.1, 2013 to Oct. 31, 2014 -- the year after -- 67 of 739 patients, or 9.1%, were readmitted within a month.

So far, so good, Waghchoure said.

But only a handful of the 739 patients -- 96 or 13.0% -- actually had PCT testing. And in that group, the results were markedly different:

Among the 63 patients with procalcitonin less than 0.25 nanograms per milliliter, 126 were readmitted, or 25.4%.

But among those with procalcitonin greater than or equal to that level, the readmission rate was just 9.1% -- -- 3 of 33 patients.

There are several possible explanation for the results, he told MedPage Today, and it will take some more work to try to tease them out.

For one thing, he said, patients with low procalcitonin might simply have been taken off their medications too early and relapsed because of it. Equally, those with higher levels would have been given a longer course of medication and might have benefited from it.

And it's even possible, he said, that some patients with low procalcitonin might not have had pneumonia at all, but other conditions instead, such as congestive heart failure or COPD.

But the study is not entirely convincing, largely because too few people were treated using the PCT algorithm, according to Muthiah Muthiah, MD, of the University of Tennessee Health Sciences Center in Memphis, who was not part of the study but who co-moderated the session at which it was presented.

"There's not a big takeaway from the study itself," he told MedPage Today. "It doesn't add much to my existing knowledge of procalcitonin."

Fewer than 20% of patients were treated using the algorithm, he noted, and although they did have a higher 30-day readmission rate, it wasn't clear whether the readmissions were early or late or what the reasons were.

On the other hand, because procalcitonin can distinguish bacterial from viral pneumonia, algorithms using it offer doctors a "huge opportunity" to reduce inappropriate antibiotic use, he said.

The study had no external support. The authors said they had nothing to disclose.

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